Process for producing beryllium



Je 1E, 1940.

B. R. F. KJELLGREN ET AL PROCESS FOR FRODUCING BERYLLIUM Filed Aug. 18, 1939 @EQUO/NG A65/V7 @RAPH/rf, come',

CO/VDf/VSE/P F/G. E.

Patented June 1l,

PROCESS FOR PRODUCING BERYLLIUM Bengt R. F. Kjellgren, Rocky River, and Charles B. Sawyer, Cleveland Heights, Ohio, assignors to The Brush Beryllium Company, Cleveland, Ohio, a corporation of Ohio Application september 1s, 1939, serial No. 295.414

4 Claims.

This invention relates to an improved process for the recovery of beryllium wherein beryllium oxide is reduced with the aid of carbonaceous reducing agents and metallic beryllium is evolved in a vapor state and relates particularly to a process in which the distilled beryllium is recovered in a highly pure state.

Attempts have heretofore been made to produce metallic beryllium by distillation in connection with the reduction of beryllium oxide with carbon, for instance by heating a mixture of beryllium oxide and carbon in an electric furnace to a temperature of the order of 2000 C. But the attempts made in this direction have not led to any useful results because the rate of reaction and evolution of beryllium under such conditions has been too slow for commercial use. Attempts have been made to increase the rate of reaction by operating in a vacuum or by owing a strong current of hydrogen through the charge, but these expedients have not improved the rate of reaction to any marked extent.

It is an object of this invention to provide a distillation process for the recovery of beryllium which is characterized by a much higher rate of reaction under commercial conditions than has heretofore been obtained.

A further object of the invention is to provide a process of the character last referred to adapted to produce metallic beryllium of a high degree of purity.

Our improved process is based upon the discovery that the rate of reaction between beryllium oxide and carbon is markedly affected by the degree of purity of the oxide. In our process of producing alloys containing beryllium set forth in our application Serial No. 89,362, filed July 7, 1936, which has matured into Patent No. 2,176.- 906, we have made use of this discovery and in our present process the discovery is taken advantage of for the production of metallic beryllium by heating a mixture of suitably pure beryllium oxide and carbon, preferablyl in stoichiometric proportions, to a temperature at which the reduced beryllium is disengaged in the form of vapor. A temperature of at least 1900 C. is necessary for this. Reduced pressure or vacuum may be resorted to, but preferably a stream of hydrogen, or other inert gas such as helium, is passed through the reaction zone. The stream of gas sweeps the beryllium vapor from the reaction zone and carries it into contact with suitable condensing means where it is cooled suddenly and thereby substantially prevented from being reoxidized by the carbon monoxide generated by the reducing reaction and carried out of the reaction zone with the beryllium vapor. Metallic beryllium is recovered in a pure condition from the condensing device, while any entrained beryllium which escapes from the condensing means may be recovered from the carbon monoxide and hydrogen Agases issuing therefrom by passing the gas through filters or centrifugal separators. If desired the hydrogen component of the gas mixture may also be recovered and recycled so as to operate the process with maximum economy.

As indicated, a stream of inert gas such as hydrogen or helium is used in the process since through its use the beryllium vapor may be swept out of the reaction zone as rapidly as it is formed, the vapor pressure of beryllium being thereby kept at such a low value that the maximum rate of reaction between the beryllium oxide and carbon is favored. Furthermore, as indicated above, the stream of gas aids in condensing the beryllium vapor without the latter being reoxidized.

As has been indicated, the present invention rests essentially upon the discovery that when high purity beryllium oxide is substitutedfor less pure oxide. the rate of production of beryllium vapor, and hence of beryllium, can be greatly increased, the increase in fact being far out of proportion to any change which might be expected from the slight change in purity of the oxide. Without wishing to be limited by the theory expressed, we believe this result is due in part to the fact that the higher purity oxide is less dense and exposes more surface to the reducing action of the carbon, and in part to the fact that by eliminating impurities such as calcium oxide, silica, alumina, and like fluxes, sintering or melting of the charge is avoided with the consequent result that the initially large area exposed by the pure oxide is not lessened when the charge is heated to the very high temperatures which must be employed, and furthermore is not diminished appreciably during any of the time that the beryllium oxide is being reduced by the carbon. A high rate of reaction may therefore be attained and maintained. Moreover, in our process the oxide and carbon mixture preferably is heated in a. loose state and the beryllium vapors disengaged by the reducing reaction are evolved in a loose, highly porous charge from which they may readily escape so as to be swept out by the current of hydrogen. The beryllium vapors accordinglydo not have opportunity to accumulate within the charge to such an extent that their concentration therein approaches the limit at which the reaction is suppressed.

'Ihe Vfollowing experimental results will illustrate the magnitude of the improvement which results when high purity oxideis substituted for lower purity material. In these experiments charges were prepared and treated in pairs, thev charges of each pair being as nearly identical as possible except for their purity, both charges containing the same. weight of oxide intimately mixed with the same proportions oi' carbonaceous reducing agent. One charge of each pair was made up with beryllium oxide containing 0.3% calcium oxide and somewhat less than 99.7% beryllium oxide, while the other charge was made up with beryllium oxide containing impurities totalling less than 0.1%, the iron oxide, calcium oxide, silica and alumina. each mounting to less than 0.02%. Both charges wereheated individually in anl induction furnace at the same rate andfor the same lengths of time and were subjected to the same rate of hydrogen iiow. In short, they were treated in identical manners, so that the purity of the oxide would be the only variable effecting a difference in the rate of evo-1 lution of beryllium from the charges.` When the charges were ltreated in this wayr'it 'was found that the rate of evolution of beryllium from the high purity sample was about double the rate of evolution from the sample containing 0.3% calcium oxide, example values of the rates being 24.5% per hour and 12.4% respectively. It will be appreciated that an increase of this magnitude in the rate of production permits extensive economies in operating costs since thetime required to produce a unit of beryllium is reduced to about half of the corresponding time required when the less pure material is used.v The improvement greatly enhances the 'commercial value of the distillation method of producing beryllium.

In practicing the present invention beryllium oxide of a suitable degree of purity can be selected, as hereinafter described, from the products now commercially available. Carbon is preferably used as reducing agent although beryllium icarbide is also suitable for use and can be used either alone or in combination with carbon. Such reducing agents as calcium carbide, calcium silicide, metallicsilicon, or silicon alloys should be avoided since they produce metallic oxides and/or silica which remain in the furnace and iiux the charge, thus creating the disadvantages which are to be avoided by the use of the high purity material. For. the same reason, carbonaceous reducing agents which contain large amounts of metallic oxides as impurities should be avoided. Graphite and resistor carbon are generally of moderate purity and are suitable for use as reducing agents. 'I'he reducing agent should, oi' course, be intimately mixed with the beryllium oxide in order to obtain the mo'st favorable conditions for eiiicient reduction, and the charge should preferably be introduced into the reaction zone in a loose, pulverulent condition, since under such conditions the stream of hydrogen may be used most effectively in maintaining a low vapor pressure of beryllium Within` the charge. The temperatures employed to effect reduction are of the same order as those heretofore proposed in connection with the use of impure starting materials, being generally above 1900 C. and preferably around 2100 C. At these temperatures various hydrocarbons, of which acetylene is an example, are formed through reaction of the hydrogen with the carbonaceous reducing agent.

Being gases at the high temperatures employed, and having strong reducing properties, these materials aid in reducing the beryllium oxide.

In the operation of the process, use may be made ci various forms and kinds of apparatus such as those heretofore usedI or proposed for use in the production of beryllium by distillation or for analogous purposes. Thus, for example, heating of the charge may be accomplished by a furnace wherein the charge is heated by high frequency induction, a carbon arc, or electrical resistance or wherein the charge forms one or `both electrodes of an electric arc. f For they purpose of further explaining and illustratingl the cedure will be accompanying drawing'.

In the drawing,

Fig. lis na. flow sheet indicating the steps of a pireferred procedure in carrying out the invent on. v

Fig. 2 is a sectional view of apparatus which may be used in selecting a suitably pure beryllium oxide by determination of its apparent density.

In describing the procedure indicated in Fig. i of the drawing, reference will rst be made to the selection of the beryllium oxide. speaking, beryllium oxidewhich is not suiiiciently pure to resist sintering at a temperature of 1600 inventionA a suitable specificv pro- C. is not suitable forthe present process, and

preferably the oxide should be pure enough to resist substantial sintering at the temperature ot the reduction reaction as carried out in the practice of the process. The troublesome impurities mostr frequently encountered in the beryllium oxide are calcium oxide and siliconoxide, though there may be others. Undecomposed sulfate may also cause trouble.

Since the density of beryllium oxide increases with increase inthe amount of impurities, a very good practical test for adequate purity of the beryllium yoxide is its apparent density. In order that the" term apparent density as herein used may have a deiinite meaning, it-is to be understood that the determination of such density is carried out in accordance with the following pro-` cedure. First, the sample of oxide used for the determination is to be heated, for the first time.

for a period of ten minutes at a temperature of 1600 C. in an atmosphere not more reducing than that oi' hydrogen. In carrying out the heat treatment, the beryllium oxide is passed through an 80 mesh screen and allowed to fall lightly into a refractory boat which is to hold itvduring the heating operation.y In Fig. 2 we have shown apparatus to be used in determining the apparent density of the heat-treated material.

ratus consists of a sieve l comprising side wall 2 and screen 3 having 20 openings per inch, the wire of of 0.0172 inch and the individualscreen openings having an area of 0.0328 square inch. The sieve is supported as shown in a large glass funnel I which in turn is suitably supported above a weighing bottle or cup 5. 'I'he full size dimensions of each piece of the apparatus are indicated in the ligure.

In making the apparent density determination after heating the sample to 1600 C. as above described, an amount of the beryllium oxide suicient to slightlyy more than fill the weighing bottle is placed upon the screen 3 and brushed through so as to fall through the funnel. without packing, into the weighing bottle the volume of which, at a height level with its top. is known. The small 'described with reference to theY Generally excess of beryllium oxide is scraped oi (without packing) to leave the material even with the bottle top. The weight of the oxide in the weighing bottle is then determined and the apparent density calculated from the known volume and the determined weight.

For the best operation of the process the apparent density of the beryllium oxide, determined as above described, should be less than 0.4. If it is greater than 0.5 the operation is unsatisfactory since considerable quantities of sintered oxide are formed, causing loss of exposed oxide surface and interfering with speedy reduction.

As a suitable procedure in practicing the method represented by Fig. 1 of the drawing, high purity oxide havingr an apparent density less than 0.5 and preferably less than 0.4 is intimately mixed with a stoichiometric amount of finely ground graphite, resistor carbon, beryllium carbide, or mixtures thereof, and the mixture is introduced in a loose condition into the reaction chamber of a suitable electric furnace and through which a current of preheated hydrogen flows, Preferably the charge is heated rapidly to a temperature above 1900 C., at which temperature the beryllium oxide is reduced by the reducing agent and yields vaporous beryllium and carbon monoxide. By reason of the stream of hydrogen owing through the reaction zone, the carbon monoxide is diluted as it and the beryllium vapor are swept out of the reaction zone. The gaseous stream may be caused to impinge on extensive cooled surfaces or otherwise treated to condense the beryllium vapor without permitting the carbon monoxide to act upon it to reoxdize it to beryllium oxide. Methods and apparatus for effecting this type of condensation are, as previously indicated, well known in the` art and form no part of the present invention. Accordingly the step is merely indicated diagrammatically in the flow sheet and need not be discussed in further detail. As indicated above, some beryllium may not be condensed in the condensing system and is carried along in the gas stream issuing therefrom. This beryllium is generallyin the form of a iine powder the particles of which are partially or fully coated with beryllium oxide and/or beryllium carbide. This powder may be separated from the gases in any 'suitable way, many of which are well known in the art. The gasstream may then be treated in known manner to recover the hydrogen which it contains, the recovered hydrogen being recycled through the process.

It will thus be seen that beryllium is recovered in at least two different forms, the material recovered from the condensing system being in a highly pure state since it is uncontaminated with any of the usual impurities which may occur in beryllium oxide and which would be vaporized and condensed along with the beryllium. The other beryllium product, consisting of a ne powder containing a minor amount of metallic beryllium and a major amount of beryllium oxide or carbide, may be mixed with graphite and recycled by including it in subsequent charges which are introduced into the distillation furnace.

In the following claims, the term carbonaceous reducing agent is used to mean carbon-containing material capable of reducing beryllium oxide at the temperatures employed, and including beryllium carbide, hydrocarbons, or some form of carbon, or mixtures of these materials.

Having now explained our invention, what we claim is:

1. In a process for recovering beryllium by thermal reduction wherein beryllium oxide is decomposed by reaction with carbonaceous reducing agent at temperatures above about 1900 C. and wherein the reduced beryllium is removed from the reaction zone in vapor form and subsequently condensed, the step of using high purity beryllium oxide having an apparent density of less than 0.5.

2. In a process for recovering beryllium by thermal reduction wherein beryllium oxide is decomposed by reaction with carbonaceous reducing agent at temperatures around 2100D C., and wherein the reduced beryllium is removed from the reaction zone in vapor form and subsequently condensed, the step of using high purity beryllium oxide having an apparent density of less than 0.4.

3. In a process for producing beryllium by thermal reduction of its oxide wherein beryllium oxide is decomposed by reaction with carbonaceous reducing agent at temperatures above about 1900 C., and wherein the reduced beryllium is removed from the reaction zone in vapor form by a current of hydrogen and is subsequently condensed and recovered as metallic beryllium, the step of using high purity beryllium oxide having an apparent density of less than 0.5.

4. In a process for producing beryllium by thermal reduction of its oxide wherein beryllium oxide is decomposed by reaction with carbonaceous reducing agent at temperatures around 2100 C., and wherein the reduced beryllium is removed from the reaction zone in vapor form by a current of hydrogen and is subsequently condensed andrecovered as metallic beryllium, the step of using high purity beryllium oxide having an apparent density of less than 0.4.

BENGT R. F. KJEILGREN. CHARLES B. SAWYEB. 

